Effect of moisture and temperature on the extrudate properties of milkfish (Chanos chanos) feed

The present study evaluated the effect of varying levels of moisture and temperature on the extrudate properties of the milkfish (Chanos chanos) feed containing 31.49% protein and 4.71% lipid. Two trials were conducted in a pilot scale twin screw extruder using 3 mm die. In the first trial, the effect of temperature on extrudate properties was studied at five different temperatures viz., 80-90, 90-100, 100-110, 110-120 and 120-130°C. The results revealed that the temperature levels of 100-110, 110-120 and 120-130°C resulted in significantly (p<0.05) lower bulk density (BD) of the extrudate than at 80-90 and 90-100°C. Significantly (p<0.05) lower water solubility index (WSI) was recorded at 100-110°C, while further increase in temperature failed to show further reduction in water solubility. The pellet durability index (PDI) and expansion ratio (ER) showed a non-significant difference among the extrudates at 100-110, 110-120 and 120-130°C. In the second trial, the effect of additional moisture on the extrudate was evaluated by including water at 20, 25, 30 and 35% and the results revealed that 30% moisture addition resulted in significantly (p<0.05) lower BD, WSI and PDI of the extrudate than the other levels. The highest moisture level of 35% led to difficulty in operation while the lower levels from 25% failed to produce floating pellets. Results of this study infers that 30% moisture addition and a temperature of 100-110°C is optimalfor production of water stable floating milk fish feeds.